Add described audio for silent video
A video with no soundtrack is closed to blind and some low-vision viewers. G166 is the audio answer rather than the text one. Record a track describing the important content of the video, in the same language as the page and a common web audio format, then label it for what it is. The labeling is part of the technique rather than an extra, and it is in W3C's own title for it. This is a sufficient technique for 1.2.1 Audio-only and Video-only (Prerecorded) at Level A, one of three routes to that rule. The alternative route is a text description, which stays searchable and can be read at any pace. Audio suits long or atmospheric footage. Text suits instructions somebody will follow step by step.
How we find it in an audit
Our reviewers find every silent video and check whether an audio description exists, whether the player offers it plainly, and whether the offer says what it is. A track labeled only 'Audio' tells nobody it is the alternative. Then we listen against the video, checking that the narration covers what is shown rather than repeating the on-screen title.
How affected users experience it
A silent time-lapse announces itself as a video and then plays nothing. There is no soundtrack to infer from. The content is fully closed rather than partly available. A described audio track turns the same file into something they can follow, and it serves anyone whose connection or device makes watching impractical.
Passes vs. fails
Passes
The player offers 'Audio description of this video', narrating each construction phase and clearly labeled as the alternative.
Fails
A silent construction time-lapse plays with no audio track and nothing describing what it shows.
How this gets tested
The W3C publishes test rules that define what a checker looks for here.
- Audio element content has text alternativeA tool finds candidates, you decide
- Video element visual-only content has accessible alternativeA tool finds candidates, you decide
Other ways to satisfy this rule
6 guides on this site are filed under 1.2.1 Audio-only and Video-only (Prerecorded). W3C lists this one as sufficient for that rule on its own. Implement it correctly, in a way your readers' software actually supports, and the rule is met.
This guide is our interpretation of W3C technique G166: Providing audio that describes the important video content and describing it as such. W3C publishes its techniques as guidance rather than as the standard, and says so on every one of them. The success criterion is what conformance is measured against, and a technique is one documented way to meet it.